The exemplary embodiment relates generally to image processing systems and, more particularly, to a method of separating vertical and horizontal components of a rasterized image.
A printed circuit board, or PCB, is a self-contained module of interconnected electronic components found in devices ranging from common beepers, or pagers, and radios to sophisticated radar and computer systems. The circuits are generally formed by a thin layer of conducting material deposited, or “printed,” on the surface of an insulating board known as the substrate. Individual electronic components are placed on the surface of the substrate and soldered to the interconnecting circuits. Contact fingers along one or more edges of the substrate act as connectors to other PCBs or to external electrical devices such as on-off switches. A printed circuit board may have circuits that perform a single function, such as a signal amplifier, or multiple functions.
Two other types of circuit assemblies are related to the printed circuit board. An integrated circuit, sometimes called an IC or microchip, performs similar functions to a printed circuit board except the IC contains many more circuits and components that are electrochemically “grown” in place on the surface of a very small chip of silicon. A hybrid circuit, as the name implies, looks like a printed circuit board, but contains some components that are grown onto the surface of the substrate rather than being placed on the surface and soldered.
Ink-jet printing of circuits is an emerging technology that attempts to reduce the costs associated with production by replacing expensive lithographic processes with simple printing operations. By printing a pattern directly on a substrate rather than using the delicate and time-consuming lithography processes used in conventional manufacturing, a printing system can significantly reduce production costs. The printed pattern can either comprise actual features (i.e., elements that will be incorporated into the final circuit, such as the gates and source and drain regions of thin film transistors, signal lines, opto-electronic device components, etc.) or it can be a mask for subsequent semiconductor or printed circuit board processing (e.g., etch, implant, etc.).
Ink-jet printing of circuits is an emerging technology that attempts to reduce the costs associated with production by replacing expensive lithographic processes with simple printing operations. By printing a pattern directly on a substrate rather than using the delicate and time-consuming lithography processes used in conventional manufacturing, a printing system can significantly reduce production costs. The printed pattern can either comprise actual circuit features (i.e., elements that will be incorporated into the final circuit, such as the gates and source and drain regions of thin film transistors, signal lines, opto-electronic device components, etc.) or it can be a mask for subsequent semiconductor processing (e.g., etch, implant, etc.).
Several forms of printing etch masks exist. One example is that of a printed wax pattern used as a copper etch mask for creating PCBs. Another example is laser direct imaging (LDI), a maskless lithography method that is currently being used for copper etch masks on PCBs. It uses a laser to write the raster image of the pattern directly on the photoresist. In order for it to be to be cost-effective, it is necessary to have special high speed resists. Also, there is no suitable method for soldermask patterning using laser.
Typically, circuit printing involves depositing a print solution (generally an organic material) by raster bitmap along a single axis (the “print travel axis”) across a solid substrate. Print heads, and in particular, the arrangements of the ejectors incorporated in those print heads, are optimized for printing along this print travel axis. Printing of a pattern takes place in a raster fashion, with the print head making “printing passes” across the substrate as the ejector(s) in the print head dispense individual droplets of print solution onto the substrate. At the end of each printing pass, the print head makes a perpendicular shift relative to the print travel axis before beginning a new printing pass. The print head continues making printing passes across the substrate in this manner until the pattern has been fully printed.
Once dispensed from the ejector(s) of the print head, print solution droplets attach themselves to the substrate through a wetting action and proceed to solidify in place. The size and profile of the deposited material is guided by competing processes of solidification and wetting. In the case of printing phase-change materials for etch mask production, solidification occurs when the printed drop loses its thermal energy to the substrate and reverts to a solid form. In another case, colloidal suspensions such as organic polymers and suspensions of electronic material in a solvent or carrier are printed and wet to the substrate leaving a printed feature. The thermal conditions and material properties of the print solution and substrate, along with the ambient atmospheric conditions, determine the specific rate at which the deposited print solution transforms from a liquid to a solid.
Wax printers produce smaller lines in the process direction than in the cross process direction due to shooting the new drop on a partially melted drop as opposed to printing on a frozen drop. This necessitates separating the horizontal and vertical components of the image prior to printing. This can be easily done with images formed from vectors and arcs such as .dxf files, but this presents a problem for rasterized images and bitmaps.
In a typical printing process, the cell size/addressability is comparable to the spot size, thus resulting in good reproduction of the images. In the case of semiconductor fabrication processes, good spot placement accuracy (˜5 um) is desired. In order to obtain this, it is necessary to print at high addressability (4800DPI corresponding to ˜5 μm cell size), especially if the print head has unevenly spaced ejectors. When the cell size is much smaller than the spot size (e.g., cell size ˜5 um and spot size ˜50 μm), large accumulation of the printed material will be observed as shown in FIG. 1. Some regions in the figure are out of focus due to the uneven height of the printed material. Printing at a resolution (DPI) with a cell size corresponding to the spot size should yield the best results, as shown in FIG. 2. When rasterization of the image is done at high addressability and then printed, there is a large three-dimensional accumulation of the masking layer that is printed, which destroys the features that are obtained, as shown in FIG. 3. This may require decimation (removal of pixels in an orderly fashion).
Thus, a method of overcoming the above-mentioned difficulties and others is needed.